Hearing device comprising an amplifier system for minimizing variation in an acoustical signal caused by variation in gain of an amplifier

ABSTRACT

The disclosure presents a method and an amplifier system for minimizing variation in an acoustical signal caused by variation in gain of an amplifier, comprising a battery for providing a supply voltage to the amplifier, a digital signal processor for providing the acoustical signal to the amplifier, a controller unit receiving an enablement signal when the supply voltage is in an offset mode, and based on the enablement signal requesting a measured voltage during a time period, and a first analog-to-digital converter configured for measuring the supply voltage to the amplifier when receiving the request from the controller unit or the first analog-to-digital converter is configured for measuring the supply voltage to the amplifier continuously, and where variations in the measured voltage relates to variations in the supply voltage during the time period. Furthermore, the controller unit is configured to predict offset modes (i.e. changes) in the supply voltage based on the enablement signals and a fitting of the measured voltages, and wherein the controller unit is configured to generate a compensating signal based on the fitting and transmit the compensating signal to the digital signal processor, the digital signal processor is then configured to minimize variation in the acoustical signal at the output of the amplifier by compensating the variation in gain of the amplifier based on the compensating signal.

TECHNICAL FIELD

The disclosure relates to an amplifier system for minimizing variationin an acoustical signal caused by variation in gain of an amplifier, infor example a hearing device.

BACKGROUND

Currently, it is known to implement a predictive feedback compensationin an amplifier for suppressing distortion caused by supply voltagevariations and output amplitude switching. A predictive step in thepredictive feedback compensation can include measuring a varying oralternating current component of a supply voltage to predict an outputpulse amplitude error for a pulse width modulator (PWM) input signalbased on a prior PWM output signal, or the predictive step can alsoinclude measuring a varying or alternating current component of anoutput pulse amplitude for the PWM output signal to predict the outputpulse amplitude error for the PWM input signal based on a prior PWMoutput signal.

It is further known to apply a predictive feedback system including acompensation circuitry for compensating for variations in a first and asecond voltage in response to a measured average of a first and a secondvoltage and a measured difference between the first and second voltages.Measuring circuitry measures the average and the difference of the firstand second voltages

U.S. Pat. No. 7,800,437 B2 discloses a method and system for closed loopfeedback for pulse width modulated switching amplifiers using predictivefeedback compensation for suppressing distortion caused by supplyvoltage variations.

WO 2004/062089 A2 discloses a delta-sigma modulator for driving anoutput stage is disclosed. The delta-sigma modulator operates M betweenfirst and second voltages and includes a loop filter, a quantizer, and afeedback loop coupling an output of the quantizer and an input of theloop filter. The feedback loop includes compensation circuitry forcompensating for variations in the first and second voltages in responseto a measured average of the first and second voltages and a measureddifference between the first and second voltages. Measuring circuitrymeasures the average and the difference of the first and secondvoltages.

SUMMARY

An object of the present disclosure is to provide an amplifier systemwhich improves the compensation of gain variation of an amplifier, suchas a digital amplifier, caused by variations in the supply voltage tothe amplifier.

Objects of the present disclosure are achieved by the present disclosuredescribed in the accompanying claims and as described in the following.

An object of the present disclosure is achieved by an amplifier systemfor minimizing variation in an acoustical signal caused by variation ingain of an amplifier, comprising a battery for providing a supplyvoltage to the amplifier, a digital signal processor for providing theacoustical signal to the amplifier, a controller unit receiving anenablement signal when the supply voltage may in an offset mode, andbased on the enablement signal requesting a measured voltage during atime period, and a first analog-to-digital converter configured formeasuring the supply voltage to the amplifier when receiving the requestfrom the controller unit or the first analog-to-digital converter may beconfigured for measuring the supply voltage to the amplifiercontinuously, and where variations in the measured voltage relates tovariations in the supply voltage during the time period. Furthermore,the controller unit may be configured to predict offset modes (i.e.changes) in the supply voltage based on the enablement signals and afitting of the measured voltages, and wherein the controller unit may beconfigured to generate a compensating signal based on the fitting andtransmit the compensating signal to the digital signal processor, thedigital signal processor may then be configured to minimize variation inthe acoustical signal at the output of the amplifier by compensating thevariation in gain of the amplifier based on the compensating signal.

A further object of the present disclosure is achieved by a hearingdevice comprising an amplifier system for minimizing variation in anacoustical signal caused by variation in a supply voltage to anamplifier. The amplifier system may comprise a battery configured toprovide a supply voltage to the amplifier, a digital signal processorconfigured to provide an acoustical signal to the amplifier, acontroller unit configured to receive an enablement signal when thesupply voltage may be in an offset mode, wherein the supply voltage maybe in the offset mode when the supply voltage short termly drops belowor above a supply voltage threshold, and the controller unit may furtherbe configured to transmit a request for a measured voltage during a timeperiod based on the enablement signal, and a first analog-to-digitalconverter configured to measure during the time period the supplyvoltage to the amplifier based on the request for the measured voltagetransmitted by the controller unit. The controller unit may beconfigured to determine another offset mode in the supply voltage basedon a fitting of measured voltages of the supply voltage to theamplifier, and wherein the controller unit may be configured to generatea compensating signal based on an estimation of variation in the supplyvoltage in the another offset mode provided by the fitting of themeasured voltages. Furthermore, the controller unit may be configured totransmit the compensating signal to the digital signal processor, thedigital signal processor may be configured to minimize the variation inthe acoustical signal by providing the compensating signal into theacoustical signal, wherein the compensating signal provides anamplification of the acoustical signal during another time period of theanother offset mode.

The external processing unit may be configured to measure the supplyvoltage Vcc from the battery, and based on the measured supply voltagethe external processing unit may be configured to generate theenablement signal. Additionally, the enablement signal may be generatedif the measured supply voltage Vcc may be below or above an averagesupply voltage over a given time period, i.e. the supply voltage may bein an offset mode.

Additionally, or alternatively, the external processing unit may beconfigured to either transmit or receive data packets or audio packetsor configured to detect whether the data packets or audio packets aretransmitted or received via a transceiver unit. For example, thetransceiver unit and the amplifier system may be comprised by a hearingdevice.

For example, when the external processing unit detects a transmission ora receive event of a data packer or an audio packet, the enablementsignal may be generated. The enablement signal may be generated becausethe amplifier system 1 expects a voltage drop in the supply voltage Vccdue to the transmission event or the receive event.

Additionally, or alternatively, the external processing unit may beconfigured to detect a write or a read event to a memory unit andgenerating the enablement signal based on the detected write or readevent. The enablement signal may be generated because the amplifiersystem expects a voltage drop in the supply voltage Vcc due to the writeevent or to the read event.

A user may experience the variation in the acoustical signal caused byvariation in gain of the amplifier as a degradation of the sound qualityof the acoustical signal or as disturbance/noise added to the acousticalsignal which may be uncorrelated to the user environment.

The variation in gain may be caused by variation in the supply voltageto the amplifier, and the variation in the supply voltage may be asudden drop in the supply voltage due to a sudden increase in currentdraw on the supply voltage. In for example a hearing device comprising amicrophone, a speaker, a wireless interface, a processor unit (includingthe amplifier system) and a battery for providing a supply voltage tothe components of the hearing device, the wireless interface may needmore power when transmitting or receiving a data packet or an audiopacket, and the need for more power results in an increase in currentdraw on the supply voltage. The increase in current draw results in adrop in the supply voltage affecting the performance of the amplifiersince the gain of the amplifier provided to the acoustical signal willbe reduced.

The digital signal processor for providing the acoustical signal to theamplifier may comprise multiple components for processing the acousticalsignal received by the digital signal processor. The components couldfor example be an upsamler involving interpolation of the incomingacoustical signal, a noise shaper involving quantization or bit-depthreduction of the acoustical signal (the purpose is to increase theapparent signal-to-noise ratio of the acoustical signal), and a pulsewidth modulation amplifier.

The digital signal processor and the amplifier system may be mounted ona printed circuit board (PCB) together with other external processingunits, such as an Radio-Frequency (RF) processing unit including awireless interface, such as WIFI, Bluetooth (Bluetooth Low energy)and/or telecoil. The external processing unit may be a memory unit forreading and writing data packets or audio packets. The externalprocessing unit may be any units which are relevant for a hearingdevice.

The hearing device may be a hearing aid.

The controller unit receiving the enablement signal may be configured topredict or estimate the compensating signal based on the enablementsignal and a measure of a voltage at a component within a hearingdevice. The voltage could be the supply voltage or an output voltage ofthat specific component. The component may be the amplifier, RFcircuits, or other components affecting the acoustical signal. Theenablement signal may be transmitted from an external processing unit,and where the enablement signal is indicating an event of which theexternal processing unit is in. The event of the external processingunit may for example be a wireless transmit or receive event when theexternal processing unit may be a radio-frequency processing unit.

The controller unit may include one or more compensating algorithmsadaptable to any of the components within the hearing device. Thecompensating algorithm may be based on a fitting method, such as alinear fitting, polynomial fitting or any mathematical fitting method intime or frequency domain. Additionally, the fitting method may be usedfor predicting the coming variations in the supply voltage, i.e. thenext offset modes in the supply voltage. The enablement signal mayinform the controller unit about the reasons of the variations in thesupply voltage, the amplitude and duration of the variation and the timeof when the variation occurred in the supply voltage. For example, thecontroller unit may be connected to an RF processing unit configured totransmit and receive data packet and/or audio packet, and when the RFprocessing unit receives data packet via a Bluetooth link, the variationin the supply voltage is caused by the need of more power of a Bluetoothcomponent within the RF processing unit. The need of more power of theBluetooth component affects the supply voltage to the amplifier. In thisspecific example, the controller unit may be connected to other externalprocessing units transmitting enablement signals to the controller unit.The enablement signal transmitted by the RF processing unit informs thecontroller unit the amplitude and duration of the variation in supplyvoltage and when the variation in the supply voltage occurred.Additionally, the enablement signal informs the reason of the variationin the supply voltage at a given time. Because of the informationprovided by the enablement signal, the controller unit may be able todistinguish between the variations in the supply voltage so that thecontroller unit may be able to predict the variations in the supplyvoltage caused by the received data packets of the RF processing unit.

The controller unit may be configured to receive multiple enablementsignals, including information of the event, such as a time period ofeach event, an amplitude measure of each event, the type of the eventand/or the time of when the variation in the supply voltage occurred.The multiple enablement signals may be transmitted by different externalprocessing units and received by the controller unit simultaneously orsequentially. The controller unit may be able to distinguish between theenablement signals which it may receive simultaneously or sequentially.For example, a first group of enablement signals for a first group eventis received by the controller unit sequentially and a second group ofenablement signals of a second group event is received in parallel or insequentially with the first group event. If the controller unit does notknow the type of the event of the enablement signals, the controllerunit will then mix the events from the two groups and perform a fittingof the measured voltages which will result in a less precise predictionof the coming offset modes in the supply voltage. In another example, ifthe enablement signals includes information of the event, the controllerunit knows which events/groups each enablement signals belongs too, andthereby, the controller unit may be able to perform a fitting ofvariations in the supply voltage caused by either the first or thesecond group of enablement signals. The advantage of doing this is thatthe fitting becomes more precise, and thereby, the compensation of thevariation in the supply voltage will be improved.

Additionally, if the second group of enablement signals are transmittedand received randomly by the controller unit and if the enablementsignals do not include information of the event type, the controllerunit will then perform a fitting of the first group of enablementsignals which the preciseness of the fitting will be reduced.

The first analog-to-digital converter may be configured to measure thesupply voltage to respective components of the hearing device, such asthe amplifier. The first analog-to-digital converter may further beconfigured to detect when the supply voltage is in the offset mode, i.e.the supply voltage is distorted. For example, if the supply voltagesuddenly drops below or above an average supply voltage over a giventime period then the supply voltage is in the offset mode.

A second analog-to-digital converter may be configured to detect whenthe supply voltage is in the offset mode and the time period of theevent causing the variations in the supply voltage.

The enablement signal may be generated by the second analog-to-digitalconverter when the supply voltage is in the offset mode.

The controller unit may perform a fitting based on the measured voltagesand based on the information provided by the enablement signals, and thecontroller unit is configured to predict the coming offset mode in thesupply voltage based on the fitting and the enablement signals. Theprediction of the offset mode includes the time of when the offset modewill appear in the supply voltage, the amplitude level of the variationin the offset mode and the time period of the offset mode.

The controller unit generates a compensating signal based on thepredicted offset modes and transmitting the compensating signal to thedigital signal processor. The digital signal processor is thenconfigured to minimize variation in the acoustical signal at the outputof the amplifier when the supply voltage is in the offset mode.

The acoustical signal at the output of the amplifier may be expressed bya transfer function, and the digital signal processor may be configuredto modify the transfer function by e.g. multiplying a constant which iscalculated based on the compensating signal. The digital signalprocessor may be configured to adjust the transfer function via theconstant based on the compensating signal for minimizing variation inthe acoustical signal at the output of the amplifier during an offsetmode.

The transfer function is a mathematical function giving thecorresponding output value of for example the amplifier or a speaker foreach possible value of the acoustical signal entering the digital signalprocessor.

Alternatively, the transfer function is a mathematical function givingthe corresponding input value of for example the amplifier or a speakerfor each possible value of the acoustical signal entering the digitalsignal processor.

The constant may be applied to the transfer function in order to providea gain to the acoustical signal expressed by the transfer function. Thegain may be provided by a multiplier.

The enablement signal is for indicating possible disturbances in thesupply voltage caused by e.g. changed current draw from functionalentities like a RF processing unit, a memory, etc. The enablement signalmay comprise further information such as the type of event, i.e. theevent which causing the disturbances, the time period of eachdisturbances and the expected amplitude of each disturbance so that thecontroller unit is able to know how the level of compensation is neededduring an offset mode in the supply voltage. The time period tells thecontroller unit the time period for the compensation to be performed.The type of event may for example be, read or write events of a memory,or transmits or receive events of a wireless interface. The type eventinformation helps the controller unit to distinguish between thereceived enablement signals and to improve the fitting of measuredsupply voltage variations.

An external processing unit supplied by the same battery as theamplifier may be configured to generate the enablement signal to thecontroller unit. The external processing unit may be an RF processingunit, a memory unit or any kind of a processing unit within a hearingdevice.

The external processing unit may be configured to provide the enablementsignal when the external processing unit performs an event, such as awireless transmit or receive event, a memory write or read event orother event that cause pulsed current draw on the supply voltage causingsupply voltage variation on the supply voltage to the amplifier. Theexternal processing unit may be connected directly or indirectly to thecontroller unit.

The enablement signal determines the time period indicating a timeperiod of the transmit or receive event or indicating a time period ofthe write or read event of the memory unit. The determined time periodmay be based on a time period of an event of any components within ahearing device.

The enablement signal may further determine the time of when the eventstarts.

The fitting may be based on a fitting of measured amplitudes of thevariations in the supply voltage as a function of a second parameterand/or based on a fitting of measured time periods of the respectivemeasured amplitudes as a function of the second parameter, where thesecond parameter may be a measure of time of when the supply voltage ismeasured.

The acoustical signal at the output of the amplifier may be expressed bya transfer function, and the digital signal processor may be configuredto modify the transfer function by, e.g. multiplying a constant which iscalculated based on the compensating signal, and where the digitalsignal processor may be configured to vary the constant based on thecompensating signal for minimizing variation in the acoustical signal atthe predicted offset modes at the output of the amplifier.

A second analog-to-digital converter may be configured to detect thetime period of when the supply voltage is in the offset mode andtransmitting the enablement signal in digital domain to the controllerunit. The second analog-to-digital converter may be implemented on thesame printed circuit board as the first analog-to-digital converter.

The measured voltage may be sampled on the supply voltage to theamplifier or on the output of the amplifier.

In a classical feedback compensation amplifier system the speed ofsampling on the supply voltage is crucial, however, in the disclosedamplifier system, which is based on an adjusted feed forwardcompensation, the speed of sampling on the supply voltage or on theoutput of the amplifier is not that crucial as in the feedback solution.Thereby, the disclosed amplifier system is more robust and stabilecompared to a regular feedback solution.

The digital signal processor comprises a noise shaper for quantizing theacoustical signal before transmitting the acoustical signal to theamplifier, and wherein the noise shaper receives the compensatingsignal.

The fitting of the measured supply voltages may be a linear fitting,polynomial fitting or any mathematical fitting method.

The enablement signal informs the controller unit the event of theenablement signal, and the controller unit may then be configured todistinguishing between the received enablement signals and performing afitting of the measured voltages which are relevant for a specificevent, such as a transmit, receive, write or read event.

A further object of the present disclosure is achieved by a method forminimizing variation in an acoustical signal caused by variation in gainof an amplifier, comprising;

-   -   providing a supply voltage to the amplifier,    -   providing the acoustical signal to the amplifier,    -   receiving an enablement signal when the supply voltage is in an        offset mode, and requesting a measured voltage in digital domain        during a time period based on the enablement signal,    -   measuring the supply voltage to the amplifier when receiving the        request from the controller unit, where variations in the        measured voltage relates to variations in the supply voltage        during the time period    -   generating a compensating signal based on the measured variation        in the voltage during the time period,    -   transmitting the compensating signal to the digital signal        processor, and    -   minimizing the variation in the acoustical signal at the output        of the amplifier during the time period by compensating the        variation in gain of the amplifier based on the compensating        signal.

The generation of the enablement signal may be provided by an externalprocessing unit which is supplied by the same battery as the amplifier.

A hearing device may comprise the amplifier system as described above.

BRIEF DESCRIPTION OF DRAWINGS

The objects of the disclosure may be best understood from the followingdetailed description taken in conjunction with the accompanying figures.The figures are schematic and simplified for clarity, and they just showdetails to improve the understanding of the claims, while other detailsare left out. Throughout, the same reference numerals are used foridentical or corresponding parts. The individual features of each objectmay each be combined with any or all features of the other objects.These and other objects, features and/or technical effect will beapparent from and elucidated with reference to the illustrationsdescribed hereinafter in which:

FIG. 1, shows an example of an amplifier system,

FIG. 2, shows an example of a timing diagram of the amplifier,

FIG. 3, shows an example of a timing diagram,

FIG. 4, shows an example of the amplifier system,

FIGS. 5A and 5B, show an example of a fitting,

FIG. 6, shows an example of the amplifier system,

FIG. 7, shows an example of the amplifier system,

FIG. 8, shows an example of the amplifier system in a hearing device,

FIG. 9, illustrates a flow diagram of a method.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations. Thedetailed description includes specific details for the purpose ofproviding a thorough understanding of various concepts. However, it willbe apparent to those skilled in the art that these concepts may bepracticed without these specific details. Several objects of theapparatus and methods are described by various blocks, functional units,modules, components, circuits, steps, processes, algorithms, etc.(collectively referred to as “elements”). Depending upon particularapplication, design constraints or other reasons, these elements may beimplemented using electronic hardware, computer program, or anycombination thereof.

A hearing device may include a hearing aid that is adapted to improve oraugment the hearing capability of a user by receiving an acoustic signalfrom a user's surroundings, generating a corresponding audio signal,possibly modifying the audio signal and providing the possibly modifiedaudio signal as an audible signal to at least one of the user's ears.The “hearing device” may further refer to a device such as an earphoneor a headset adapted to receive an audio signal electronically, possiblymodifying the audio signal and providing the possibly modified audiosignals as an audible signal to at least one of the user's ears. Suchaudible signals may be provided in the form of an acoustic signalradiated into the user's outer ear, or an acoustic signal transferred asmechanical vibrations to the user's inner ears through bone structure ofthe user's head and/or through parts of middle ear of the user orelectric signals transferred directly or indirectly to cochlear nerveand/or to auditory cortex of the user.

The hearing device is adapted to be worn in any known way. This mayinclude i) arranging a unit of the hearing device behind the ear with atube leading air-borne acoustic signals or with a receiver/loudspeakerarranged close to or in the ear canal such as in a Behind-the-Ear typehearing aid or a Receiver-in-the Ear type hearing aid, and/or ii)arranging the hearing device entirely or partly in the pinna and/or inthe ear canal of the user such as in a In-the-Ear type hearing aid orIn-the-Canal/Completely-in-Canal type hearing aid, or iii) arranging aunit of the hearing device attached to a fixture implanted into theskull bone such as in Bone Anchored Hearing Aid or Cochlear Implant, oriv) arranging a unit of the hearing device as an entirely or partlyimplanted unit such as in Bone Anchored Hearing Aid or Cochlear Implant.

A hearing device may be part of a “hearing system”, which refers to asystem comprising one or two hearing devices, disclosed in presentdescription, and a “binaural hearing system” refers to a systemcomprising two hearing devices where the devices are adapted tocooperatively provide audible signals to both of the user's ears. Thehearing system or binaural hearing system may further include auxiliarydevice(s) that communicates with at least one hearing device, theauxiliary device affecting the operation of the hearing devices and/orbenefitting from the functioning of the hearing devices. A wired orwireless communication link between the at least one hearing device andthe auxiliary device is established that allows for exchanginginformation (e.g. control and status signals, possibly audio signals)between the at least one hearing device and the auxiliary device. Suchauxiliary devices may include at least one of remote controls, remotemicrophones, audio gateway devices, mobile phones, public-addresssystems, car audio systems or music players or a combination thereof.The audio gateway is adapted to receive a multitude of audio signalssuch as from an entertainment device like a TV or a music player, atelephone apparatus like a mobile telephone or a computer, a PC. Theaudio gateway is further adapted to select and/or combine an appropriateone of the received audio signals (or combination of signals) fortransmission to the at least one hearing device. The remote control isadapted to control functionality and operation of the at least onehearing devices. The function of the remote control may be implementedin a SmartPhone or other electronic device, the SmartPhone/electronicdevice possibly running an application that controls functionality ofthe at least one hearing device.

In general, a hearing device includes i) an input unit such as amicrophone for receiving an acoustic signal from a user's surroundingsand providing a corresponding input audio signal, and/or ii) a receivingunit for electronically receiving an input audio signal. The hearingdevice further includes a signal processing unit for processing theinput audio signal and an output unit for providing an audible signal tothe user in dependence on the processed audio signal.

The input unit may include multiple input microphones, e.g. forproviding direction-dependent audio signal processing. Such directionalmicrophone system is adapted to enhance a target acoustic source among amultitude of acoustic sources in the user's environment. In one object,the directional system is adapted to detect (such as adaptively detect)from which direction a particular part of the microphone signaloriginates. This may be achieved by using conventionally known methods.The signal processing unit may include amplifier that is adapted toapply a frequency dependent gain to the input audio signal. The signalprocessing unit may further be adapted to provide other relevantfunctionality such as compression, noise reduction, etc. The output unitmay include an output transducer such as a loudspeaker/receiver forproviding an air-borne acoustic signal transcutaneously orpercutaneously to the skull bone or a vibrator for providing astructure-borne or liquid-borne acoustic signal. In some hearingdevices, the output unit may include one or more output electrodes forproviding the electric signals such as in a Cochlear Implant.

It should be appreciated that reference throughout this specification to“one embodiment” or “an embodiment” or “an object” or features includedas “may” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the disclosure. Furthermore, the particular features,structures or characteristics may be combined as suitable in one or moreembodiments of the disclosure. The previous description is provided toenable any person skilled in the art to practice the various objectsdescribed herein. Various modifications to these objects will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other objects.

The claims are not intended to be limited to the objects shown herein,but is to be accorded the full scope consistent with the language of theclaims, wherein reference to an element in the singular is not intendedto mean “one and only one” unless specifically so stated, but rather“one or more.” Unless specifically stated otherwise, the term “some”refers to one or more.

Accordingly, the scope should be judged in terms of the claims thatfollows.

FIG. 1 shows an example of an amplifier system 1 comprising a battery 10transferring a supply voltage (Vcc) 20 to an amplifier 18. A digitalsignal processor (DSP) 12 is connected to the amplifier 18 where the DSPtransfer an acoustical signal 6 received from for example a microphone41 (not shown in this figure). Furthermore, the DSP may be configured toreceive multiple acoustic signals from multiple microphones (again, notshown in this figure). The amplifier 18 receives at the input 24 theacoustical signal 6 and applies a gain to the acoustical signal 6. Theamplifier 18 may then transfer the amplified acoustical signal via theamplifier output (Vout) 8 to for example a receiver 43 (e.g. a speaker,not shown in this figure). A controller unit 14 is connected to the DSP12 and a first analog-to-digital converter 16. The controller unit 14 isconfigured to receive an enablement signal 4 and then requesting ameasured voltage in digital domain and during a time period based on theenablement signal. The first analog-to-digital converter 16 receivesthen the request from the controller unit and measures 8 the supplyvoltage to the amplifier 18 The measured voltage is then transmitted tothe controller unit. The controller unit performs a fitting based on themeasured voltages and based on the information provided by theenablement signals, and the controller unit predicts then the comingoffset mode in the supply voltage based on the fitting and theenablement signals. The prediction of the offset mode, which is based onthe fitting, includes the time of when the offset mode will appear inthe supply voltage, the amplitude level of the variation in the offsetmode and the time period of the offset mode.

The compensation signal 2 is provided based on the fitting to thedigital signal processor 12. The digital signal processor 12 is thenconfigured to minimize variation in the acoustical signal 6 at theoutput 22 of the amplifier 8 when the supply voltage 20 is in an offsetmode 52 which is predicted by the controller unit 14.

FIG. 2 shows an example of a timing diagram of the amplifier system 1without an enablement signal. An event 51 of an external processing unit30 may represent a transmission or receive of multiple data packets oraudio packets 51 with different amplitude levels 37 and time periods (T₁to T₈) and at different times 36. For example, at time period T₁ theexternal processing unit 30 transmits a data packet during a time periodT₁ with an amplitude level 37 and at a time 36. It is seen that theamplitude level 37 in the supply voltage 20 drops because of the eventin the external processing unit 30. The time period of the drop iseither equal to or similar to the time period of the event of theexternal processing unit 30. The supply voltage is in an offset mode 52when the supply voltage short termly drops below or above for example asupply voltage threshold. The supply voltage threshold may be determinedby the average supply voltage of the battery as being between +/−0.1% to+/−10%, +/−1% to +/−25% or +/−0.05% to +/−5% of the average supplyvoltage. The average supply voltage varies proportional to the depletionof the battery. In this particular example the supply voltage hasdropped below the supply voltage threshold at T₁ to T₈. The acousticalsignal at the output of the amplifier 22 experiences a drop 53 in theamplitude level 37 when the supply voltage 20 experience a drop 52. Inthis particular example the user would experience a poor audio qualityof the acoustical signal.

FIG. 3 shows an example of a timing diagram of the amplifier system 1including an enablement signal 4. The example is similar to the onedisclosed in FIG. 2, enablement signals 4 are generated at a specifictime 36 representing an event 51 of the external processing unit 30.Each enablement signal 4 includes information of an event includingamplitude level 34 (A₁ or A₂), a time period (T₁ to T₈) 32 and a time 36which is measure of when the event occurred. As explained before, thecontroller unit 14 receives information about the variation 52 on thesupply voltage 20 via the enablement signal 4, and the controller isthen configured to predict when the next variations 52 in the supplyvoltage 20 will appear based on the fitting of both the amplitudesand/or time periods of the events. Based on the prediction, thecontroller unit 14 generates and transmits a compensation signal 2 tothe DSP 12. The DSP 12 provides the compensation signal 2 into theacoustical signal 6 by, e.g. multiplying a constant, depending on thecompensation signal 2, to for example a transfer function of theacoustical signal 6 going out of the amplifier 18. In this example, thecompensation results in an amplification of the acoustical signal 6 atpredicted times 39, and within the predictive time periods (T₉ to T₁₆),and with predictive amplification levels. The amplification at eachpredicted time 39 and time periods (T₉ to T₁₆) are different. Theamplification is depending on the amount of power needed to process therespective predicted events. The amplified acoustical signal, at thepredicted events (T₉ to T₁₆) enters the amplifier 18 and at the output22 of the amplifier 18 the variations 53 in the acoustic signal outputof the amplifier 22 have been eliminated or reduced resulting inacoustical signals 6 which will sound unaffected by the variations 53 inthe supply voltage 20.

FIG. 4 shows an example of the amplifier system 1, where the enablementsignal 4 is provided by the external processing unit 30 configured toeither transmit or receive 38 data packets or audio packets, or write orread 40 to a memory unit. The external processing unit 30 may beconfigured to any events 42 within a hearing device. In this example,the external processing unit 30 may be configured to measure the supplyvoltage Vcc from the battery 10, and based on the measured supplyvoltage the external processing unit 30 is configured to generate theenablement signal 4. Additionally, the enablement signal 4 may begenerated if the measured supply voltage Vcc is below or above anaverage supply voltage over a given time period, i.e. the supply voltageis in an offset mode.

Additionally, or alternatively, the external processing unit 30 may beconfigured to either transmit or receive 38 data packets or audiopackets or configured to detect whether the data packets or audiopackets are transmitted or received 38 via a transceiver unit (not shownin this figure). For example, the transceiver unit and the amplifiersystem 1 may be comprised by a hearing device. For example, when theexternal processing unit 30 detects a transmission or a receive 38 eventof a data packer or an audio packet, the enablement signal 4 isgenerated. The enablement signal 4 is generated because a voltage dropin the supply voltage Vcc will appear due to the transmission event 38or the receive event 38 if no compensation is provided to the gain ofthe amplifier 18.

Additionally, or alternatively, the external processing unit 30 may beconfigured to detect a write or a read event 40 to a memory unit andgenerating the enablement signal a voltage drop in the supply voltageVcc will appear due to the write event 40 or to the read event 40 if notcompensation is provided to the gain of the amplifier 18.

FIG. 5A and 5B show an example of the controller unit 14 predicting thenext offset modes based on a fitting 44 of measured amplitudes 34 of themeasured voltages (8A to 8H) as a function of a second parameter (whichin this example is the time 36) and/or based on a fitting of measuredtime periods (T₁-T₈) of the respective measured amplitudes (8A to 8H,34) as a function of the second parameter, where the second parametermay be the time 36. The time 36 may be a measure of when the measuredhas been performed, or when the enablement signal is received, or whenan event of an external processing unit 30 has occurred.

FIG. 5A shows that the fitting 44 of the measured voltages (8A to 8H)are divided into two groups, each group representing an event. In thisexample a first group event 45A comprises measured amplitudes 34 ofmeasured voltages (8A, 8B, 8E and 8F) when the external processing unit30 is transmitting data packets. The group of events further comprises asecond group event 45B comprising measured amplitudes 34 of measuredvoltages (8C, 8D, 8G and 8H) when the external processing unit 30 isreceiving data packets. The first group event 45A may represent an eventof a first external processing unit being a memory unit doing a memorywrite procedure, and the second group event 45B may represent an eventof a second external processing unit being a RF processing unit doing areceive of data packet event.

By dividing the measured voltages (8A to 8H) into group events resultsin an improved fitting of respective events, and thereby, the controllerunit is able to predict more precise for the coming events the amount ofpower the events are drawing from the battery, and which in this examplewill result in a more precise estimation of how much amplificationshould be provided to the acoustical signal for each predicted events(i.e. predicted offset modes in the supply voltage, 20).

FIG. 5B shows a similar example as explained in FIG. 5A, but where thefitting is based on the measured time periods (T₁-T₈) of the measuredvoltages (8A to 8H) of each events. The events are divided into a firstgroup event 45A and a second group event 45B for events similar to theexample in FIG. 5A.

By dividing the measured voltages (8A to 8H) into group events resultsin an improved fitting of respective events, and thereby, the controllerunit is able to predict more precise the time period of eachamplification (8A to 8H, 34) for the next offset modes.

FIG. 6 shows an example of the amplifier system 1, where in this examplethe enablement signal 4 is generated by a second analog to digitalconverter 17. The second analog-to-digital converter 17 is configured todetect the time period (T₁ to T₈) of when the supply voltage is in theoffset mode 52 and transmitting the enablement signal 4 in digitaldomain to the controller unit 14. The enablement signal 4 is generatedby the second analog-to-digital converter 17 when the supply voltage isin the offset mode 52.

FIG. 7 shows the amplifier system 1 where the enablement signal 4 iseither provided by the external processing unit 30 described in FIG. 4,or the second analog-to-digital converter 17 described in FIG. 6. Inthis particular example the compensating signals 2 is transmitted to amultiplier within the digital signal processor and then forwarded to anoise shaper 46 within the digital signal processor 12. Thereby, thedelay of performing the compensation is reduced. The multiplier providesa gain to the acoustical signal, wherein the gain is determined by thecompensating signals 2. Again, the controller unit 14 can be connectedwith multiple external processing units.

FIG. 8 shows the amplifier system 1 in a hearing device, where theenablement signal 4 is generated by the external processing unit 30and/or the second analog-to-digital converter 17. The acoustical signal6 is generated by a microphone 41 and transmitted into an upsampler 47.Furthermore, the digital signal processor 12 comprises a pulse widthmodulator 48 and a third analog-to-digital converter 49. The compensatedacoustical signal output 22 of the amplifier 18 is received by a speaker43.

The amplifier system 1 described in FIGS. 1 to 8 may be comprised by ahearing device, such as a hearing aid, a headphone or a headset.

FIG. 9 illustrates a flow diagram of a method 50 for minimizingvariation in the acoustical signal 6 caused by variation in gain of theamplifier 18. The method comprising; providing a supply voltage to theamplifier 50A, providing the acoustical signal to the amplifier 50B,receiving an enablement signal when the supply voltage is in an offsetmode 50C, and requesting a measured voltage in digital domain during atime period based on the enablement signal 50D, measuring the voltage tothe amplifier when receiving the request from the controller unit 50E,where variations in the measured voltage relates to variations in thesupply voltage during the time period, predicting offset modes in thesupply voltage based on a fitting of the measured voltages 50F,generating a compensating signal based on the fitting 50G, transmittingthe compensating signal to the digital signal processor 50H, andminimizing the variation at the predicted offset modes in the acousticalsignal at the output of the amplifier by compensating the variation ingain of the amplifier based on the compensating signal 50I.

The method 50 comprises a transmission of the enablement signal from anexternal processing unit 30 or a second analog-to-digital converter 17.

1. A hearing device comprising an amplifier system for minimizingvariation in an acoustical signal caused by variation in a supplyvoltage to an amplifier, wherein the amplifier system comprising; abattery configured to provide a supply voltage to the amplifier, adigital signal processor configured to provide an acoustical signal tothe amplifier, a controller unit configured to receive an enablementsignal when the supply voltage is in an offset mode, wherein the supplyvoltage is in the offset mode when the supply voltage short termly dropsbelow or above a supply voltage threshold, and the controller unit isfurther configured to transmit a request for a measured voltage during atime period based on the enablement signal, and a firstanalog-to-digital converter configured to measure during the time periodthe supply voltage to the amplifier based on the request for themeasured voltage transmitted by the controller unit, and wherein thecontroller unit is configured to determine another offset mode in thesupply voltage based on a fitting of measured voltages of the supplyvoltage to the amplifier, and wherein the controller unit is configuredto generate a compensating signal based on an estimation of variation inthe supply voltage in the another offset mode provided by the fitting ofthe measured voltages, and the controller unit is configure to transmitthe compensating signal to the digital signal processor, the digitalsignal processor is configured to minimize the variation in theacoustical signal by providing the compensating signal into theacoustical signal, wherein the compensating signal provides anamplification of the acoustical signal during another time period of theanother offset mode.
 2. A hearing device according to claim 1, whereinan external processing unit supplied by the same battery as theamplifier is configured to generate the enablement signal to thecontroller unit.
 3. A hearing device according to claim 2, wherein theexternal processing unit is configured to provide the enablement signalwhen the external processing unit performs an event, such as a wirelesstransmit or receive event or a memory write or read event.
 4. A hearingdevice according to claim 3, wherein the time period is a time period ofthe transmit or receive event or a time period of the memory write orread event or a time period of a measurement of the supply voltage.
 5. Ahearing device according to claim 1, wherein the fitting is based on afitting of measured amplitudes of the measured voltages of supplyvoltage to the amplifier as a function of a second parameter and/orbased on a fitting of measured time periods of the respective measuredamplitudes as a function of the second parameter, where the secondparameter is a time of when the supply voltage is measured.
 6. A hearingdevice according to claim 1, wherein the acoustical signal at the outputof the amplifier is expressed by a transfer function, and the digitalsignal processor is configured to modify the transfer function byintroducing a constant which is calculated based on the compensatingsignal into the transfer function, and where the digital signalprocessor is configured to vary the constant based on the compensatingsignal for minimizing variation in the acoustical signal caused byvariation in the gain of the amplifier.
 7. A hearing device according toclaim 1, wherein a second analog-to-digital converter is configured todetect the time period of when the supply voltage is in the offset mode,and wherein the second analog-to-digital converter is configured totransmit the enablement signal in digital domain to the controller unit.8. An hearing device according to claim 1, wherein the firstanalog-to-digital converter is configured to sample the supply voltageto the amplifier or on the output of the amplifier.
 9. A hearing deviceaccording to claim 1, wherein the digital signal processor comprises anoise shaper configured to quantize the acoustical signal beforetransmitting the acoustical signal to the amplifier, and wherein thenoise shaper is further configured to receive the compensating signal.10. A hearing device according to claim 1, wherein the fitting of themeasured supply voltages is based on a linear fitting, polynomialfitting or any mathematical fitting method.
 11. A hearing deviceaccording to claim 3, wherein the enablement signal is configured toinform the controller unit the event of the enablement signal, and thecontroller unit is configured to distinguish between the receivedenablement signals and performing a fitting of the measured voltageswhich are relevant for a specific event.
 12. A method for minimizingvariation in an acoustical signal caused by variation in a supplyvoltage to an amplifier, comprising; providing a supply voltage to theamplifier, providing an acoustical signal to the amplifier, receiving anenablement signal when the supply voltage is in an offset mode, whereinthe supply voltage is in the offset mode when the supply voltage shorttermly drops below or above a supply voltage threshold, and requesting ameasured voltage during a time period based on the enablement signal,measuring the supply voltage to the amplifier when receiving the requestfrom the controller unit, where variations in the measured voltagerelates to variations in the supply voltage during the time period,determining another offset mode in the supply voltage based on a fittingof measured voltages of the supply voltage to the amplifier, generatinga compensating signal based on an estimation of variation in the supplyvoltage in the another offset mode provided by the fitting of themeasured voltages, transmitting the compensating signal to the digitalsignal processor, and minimizing the variation in the acoustical signalby providing the compensating signal into the acoustical signal, whereinthe compensating signal provides an amplification of the acousticalsignal during another time period of the another offset mode.
 13. Amethod according to claim 12, wherein the generation of the enablementsignal is provided by an external processing unit which is supplied bythe battery as the amplifier.
 14. A method according to claim 13,wherein the external processing unit is configured to provide theenablement signal when in a wireless transmit or receive event or whenin a write or read event
 15. A method according to claim 12, wherein thecontroller unit is configured to estimate the compensating signal basedon a fitting of measured amplitudes of the measured supply voltages as afunction of a time when receiving the enablement signal.
 16. A hearingdevice according to claim 1, wherein the hearing device is a hearingaid.
 17. A hearing device according to claim 2, wherein the fitting isbased on a fitting of measured amplitudes of the measured voltages ofsupply voltage to the amplifier as a function of a second parameterand/or based on a fitting of measured time periods of the respectivemeasured amplitudes as a function of the second parameter, where thesecond parameter is a time of when the supply voltage is measured.
 18. Ahearing device according to claim 3, wherein the fitting is based on afitting of measured amplitudes of the measured voltages of supplyvoltage to the amplifier as a function of a second parameter and/orbased on a fitting of measured time periods of the respective measuredamplitudes as a function of the second parameter, where the secondparameter is a time of when the supply voltage is measured.
 19. Ahearing device according to claim 4, wherein the fitting is based on afitting of measured amplitudes of the measured voltages of supplyvoltage to the amplifier as a function of a second parameter and/orbased on a fitting of measured time periods of the respective measuredamplitudes as a function of the second parameter, where the secondparameter is a time of when the supply voltage is measured.
 20. Ahearing device according to claim 2, wherein the acoustical signal atthe output of the amplifier is expressed by a transfer function, and thedigital signal processor is configured to modify the transfer functionby introducing a constant which is calculated based on the compensatingsignal into the transfer function, and where the digital signalprocessor is configured to vary the constant based on the compensatingsignal for minimizing variation in the acoustical signal caused byvariation in the gain of the amplifier.